1. Field of the Invention
The present invention relates to ink jet recording method and apparatus, that are used for printers, copying machines, facsimile machines, word processors and the like.
2. Description of the Related Art
In principle, ink jet recording is carried out by ejecting droplets of a liquid or molten solid ink from a nozzle, a slit or a porous film and the like, to thereby record onto a printing medium such as paper, fabric or film. In order to eject ink, various methods have been proposed such as the so-called static control method, utilizing static attraction, the method utilizing oscillation pressure of a piezoelectric element; and the so-called heat ink jet method, which utilizes pressure that is generated from air bubble formation and growth with heat. By employing these methods, images with a remarkably high level of detail can be created.
Ink jet recording apparatuses have been extensively examined since they provide advantages such as being compact, inexpensive and quiet. Recently, ink jet recording apparatuses capable of high-quality printing like a monochrome printer which forms black images and a color printer which provides full-color images have come to be widely sold. These printers can record on plain paper such as writing paper or copier paper, and occupy a major portion of the printing apparatus market.
The ink for ink jet recording used in the ink jet apparatuses must be able to achieve the following:    (1) provide images having high resolution, high density and uniformity, without bleeding or fogging on paper;    (2) cause no clogging at the tip of the nozzle due to dried ink, and exhibiting good ejecting responsiveness and good ejecting stability;    (3) be quick-drying on paper;    (4) provide fastness of images; and    (5) possess good long-term storability.
In particular, with the recent rise in printing speeds, there has been a demand for a quick-drying ink capable of providing very high-quality images even when recording is carried out on plain paper such as copier paper.
Further, as an ink jet recording ink, ink that mainly contains a dye as color material has been used. However, the ink using a dye has deteriorated water resistance and light fastness of an image. In order to solve these problems, an ink that contains a pigment as the color material has been considered.
In order to correspond to the recent rise in printing speeds, a method of expediting the drying of ink has also been carried on. However, if the drying of ink is simply quickened, deterioration of image density is caused. To this end, a method has been considered in which inks aggregate on recording paper due to a reaction between the inks to thereby improve the image density.
For example, Japanese Patent Application Laid-Open (JP-A) No. 2001-294788 discloses an inkjet recording method in which a color ink is printed in a printing area of a black ink using an ink set in which the drying time of each of the black ink and the color ink is 5 seconds or less and the color ink contains a coagulating agent that aggregates components in the black ink.
The above-described method disclosed by JP-A No. 2001-294788 has achieved quick drying of a printed image and a high optical density of an image, and also has solved image bleeding occurring between different colors. However, if the drying time of a black ink that contains, as a black pigment of the black ink, carbon black having excellent optical density, water resistance and light fastness is quickened, the image quality of a black image portion, such as sharpness of an image edge portion, no thickening of a line, and the like is deteriorated in the existing circumstances, and improvements therefore have been demanded.